Tom’s preview: It seems strange to say that the first game of any competition can be classed as must win.

But that appears to be what Saturday’s Champions Cup clash with Scarlets is for Saints.

Not because if they lose they will be out, but because of what a victory would do for Jim Mallinder’s men,

They require a shot in the arm after back-to-back defeats, to Sale and Saracens.

And that is so desperately needed ahead of a tricky trip to Scotstoun a week on Saturday.

Saints need to get some momentum and get back in the groove.

After an unbeaten pre-season campaign, illuminated by late victories against Wasps and Worcester, they have failed to find their mojo in the serious stuff.

And it doesn’t get much more serious than Europe’s premier club rugby tournament.

If there is a little margin for error in the Aviva Premiership, there is barely any breathing space in the Champions Cup.

Lose a home game and you are right up against it, especially if your next two games in the competition are at Guinness Pro12 champions Glasgow and cash-rich Racing 92, who will be able to call on All Blacks star Dan Carter among others.

So Saints don’t just need a win this weekend.

They need a win and a good performance to get the juices flowing for the following week’s trip to Scotstoun and the December double-header with Racing.

If they can do that, they can look to take some momentum back into the Premiership, in which they currently lie 10th.

Saints simply aren’t used to that sort of standing and it will have come as a shock to the system.

Fans will hope that is a good thing, with the coming weeks and months refusing to provide any respite.

Quality and composure will be required in huge measures, and Saints will be asked to show why they were top of the English pile last season.

Forget their recent form, they have the talent to do it.

But they will need to do it this weekend, otherwise their hopes of progressing to the quarter-finals for the second season in succession will be looking very slim.